Adaptive cubic interpolation of CT slices for maximum intensity projection

Three-dimensional visualization of medical images, using maximum intensity projection (MIP), requires isotropic volume data for the generation of realistic and undistorted 3-D views. However, the distance between CT slices is usually larger than the pixel spacing within each slice. Therefore, before the MIP operation, these axial slice images must be interpolated for the preparation of the isotropic data set. Of many available interpolation techniques, linear interpolation is most popularly used for such slice interpolation due to its computational simplicity. However, as resulting MIP's depend heavily upon the variance in interpolated slices (due to the inherent noise), MIP's of linearly interpolated slices suffer from horizontal streaking artifacts when the projection direction is parallel to the axial slice (e.g., sagittal and coronal views). In this paper, we propose an adaptive cubic interpolation technique to minimize these horizontal streaking artifacts in MIP's due to the variation of the variance across interpolated slices. The proposed technique, designed for near-constant variance distribution across interpolated slices, will be shown to be superior over the linear interpolation technique by completely eliminating the horizontal streaking artifacts in MIP's of simulated data set and real CT data set.